Infection with hepatitis B virus is a major cause of liver disease worldwide and accounts for 5-10% of chronic liver disease and cirrhosis in the United States. Safe and effective vaccines are now available for prevention of hepatitis B. However, therapies for the disease once it has occurred are unsatisfactory. Alpha interferon was the first antiviral agent shown to be effective in this disease and was licensed for this indication in the United States in 1993. The bases for licensure were, in part, studies conducted in the Liver Diseases Section of the NIH. Unfortunately, alpha interferon is effective in only one-third of patients with typical chronic hepatitis B and its role in atypical forms of this disease remain unclear. Current activities in the Liver Diseases Section are focused on understanding the immunopathogenesis of chronic HBV infection and developing better therapies to prevent in longterm consequences.